The need for a hygenienic shaft seal for a shaft that extends into the interior of a food processing vat and is driven from the outside of the vat is well known. To be hygeneinic, a seal for such a shaft must prevent contaminants from entering the interior of the vat during the processing of the particular food product. In addition, the seal must allow the contaminants and any residual food product to be flushed from the seal during cleaning of the vat after processing of the particular food product is complete.
U.S. Pat. No. 4,136,886 describes an arrangement for cleaning a sealing ring for use in the processing of jam that is comprised of a first and a second sealing ring adapted for rotation with the shaft that define a cleaning channel between the two rings that may be flushed with a cleaning liquid. This design has been ineffective because of problems in securing the sealing rings to the shaft and because of difficulties in maintaining the hygeinic nature of the seal due to the large number of components and crevices formed between the components that make cleaning the seal difficult. In addition, the design of and number of components of such a seal is makes the seal difficult to manufacture and repair.
Accordingly, it would be advantageous to have a hygeneinic shaft seal for a food processing vat that is easier to construct and maintain and minimizes the risk of contamination to the food in the vat, yet still allows contaminants and residual food product to be easily flushed from the seal.